1. Field of the Invention
The present invention relates to a machine usable for operations of pull-on and pull-out of a dampener cover to and from the rubber roller of offset printing press and more particularly to a machine used for fitting a water feed cover over the rubber roller constituting a main part of dampening roller adapted to feed water to the printing surface of a printing drum in the offset printing press and removing the used cover from the rubber roller to replace it with new one.
2. Description of the Prior Art
As is well known in the art of offset printing, water is fed to the printing surface of a printing drum by using dampening roller and thereafter oil based ink is fed thereto by means of a rubber roller which serves to feed printing ink.
The water dampener roller is constructed by fitting a cover having a nature of good water absorption over the whole surface of the rubber roller. The cover is usually made of knit material in the cylindrical configuration and binding strings are provided at both the open ends of the cover.
When a cover is to be fitted over the surface of a rubber roller, the one open end of the cover is previously closed by tightening the binding string but the other open end is kept opened with an operator's hands. Thereafter, the cover is fitted onto the upper end of a rubber roller standing upright on the floor by handling with both the hands of an operator, it is then drawn downwardly and finally the other open end of the cover which has reached the lower end of the rubber roller is bound about the roller shaft by tightening the binding string. Thus, a cover fitting operation is achieved.
However, due to the remarkable progress of printing technology in the recent years there has been raised a requirement for more tight fitting of a cover over the whole surface of the rubber roller. To satisfactorily meet the requirement measures are taken such that the cover is strengthened and moreover it is modified so as to exhibit a nature of highly increased contractibility when it gets wetted with water. However, it takes a long time and a large amount of manpower that the thus improved and strengthened cover is manually fitted over the whole surface of the rubber roller in the same manner as in the case of the conventional dampening roller. Therefore, it becomes hard work. When the used cover is replaced with a new one, a cutter is usually used to tear the cover which is tightly fitted to the whole surface of the rubber roller but there is a danger of damaging the rubber roller or injuring an operator.